Variable-capacity compressor

ABSTRACT

A variable-capacity compressor capable of improving starting performance of the compressor and eliminating the risk of the compressor becoming uncontrollable due to contamination or the like in a refrigerant is disclosed. An opening passage allowing the control pressure chamber to communicate with a suction chamber is provided separately from a bleed passage, a valve housing chamber is formed on the opening passage, and the opening passage is formed by including an upstream-side opening passage allowing the control pressure chamber to communicate with the valve housing chamber and a downstream-side opening passage allowing the valve housing chamber to communicate with the suction chamber. A valve body housed so as to open/close the downstream-side opening passage and a biasing means biasing the valve body in an opening direction are provided. The valve housing chamber is connected to the downstream side of a pressure control valve provided on a supply passage.

TECHNICAL FIELD

The present invention relates to a variable-capacity compressor capableof varying a discharge capacity by adjusting a pressure in a controlpressure chamber, and particularly relates to a variable-capacitycompressor including a supply passage allowing a discharge chamber tocommunicate with the control pressure chamber and a bleed passageallowing the control pressure chamber to communicate with a suctionchamber, in which an opening degree of the supply passage is adjusted bya control valve provided on the supply passage to thereby adjust thepressure in the control pressure chamber.

BACKGROUND ART

The variable-capacity compressor adopts a mechanism in which a tiltangle of the swash plate is changed and piston stroke amounts areadjusted by adjusting the pressure of the control pressure chamber tothereby vary the discharge capacity. As such compressor, a structure isknown, in which the discharge chamber is allowed to communicate with thecontrol pressure chamber through the supply passage, the controlpressure chamber is allowed to constantly communicate with the suctionchamber through the bleed passage, the opening degree of the supplypassage is adjusted by the control valve provided on the supply passageand a refrigerant amount flowing into the control pressure chamber isadjusted to thereby control the pressure in the control pressurechamber.

In the above structure, when the supply passage is blocked by thecontrol valve, a high-pressure gas is not introduced from the dischargechamber to the control pressure chamber and the control pressure chamberconstantly communicates with the suction chamber through the bleedchamber, therefore, the pressure in the control pressure chamber isreduced to approximately the same value as a pressure in the suctionchamber, and the compressor is operated at the maximum capacity. Whenthe supply passage is opened by the control valve, the high-pressure gasin introduced from the discharge chamber to the control pressure chamberand a refrigerant gas flows out from the control pressure chamber to thesuction chamber through the bleed passage, however, the pressure in thecontrol pressure chamber is increased, therefore, the discharge capacityof the compressor is controlled by adjusting the opening degree of thesupply passage by the control valve.

Incidentally, when the compressor is suspended for a long time withoutbeing operated, the pressure in a refrigerating cycle is balanced aswell as a refrigerant in the refrigerating cycle becomes liquid at aportion of the lowest temperature in the refrigerating cycle. Thecompressor has the highest heat capacity in elements forming therefrigerating cycle and is not easily heated following variation ofoutdoor temperature, therefore, the phenomenon in which the refrigerantin the refrigerating cycle becomes liquid inside the compressor occurs.When the refrigerant becomes liquid inside the compressor, a liquidrefrigerant is accumulated also in the control pressure chamber.

When the compressor is started from the state where the pressure isbalanced, the pressure in the suction chamber is reduced by operation ofthe compressor, and a refrigerant in the control pressure chamber isdischarged to the suction chamber through the bleed passage inaccordance with the reduction of the pressure. However, when the liquidrefrigerant is accumulated in the control pressure chamber, the insideof the control pressure chamber is in the balanced state in which both agas-phase refrigerant and a liquid-phase refrigerant exist, therefore,the pressure in the control pressure chamber is maintained in asaturated pressure even when the refrigerant in the control pressurechamber is discharged to the suction chamber through the bleed passage.Accordingly, there has been known an inconvenience that the pressure inthe control pressure chamber is not reduced until all the liquidrefrigerant is vaporized and is discharged from the bleed passage and itis difficult to perform control of the discharge capacity (to increasethe discharge capacity).

In order to solve the above problems, a structure shown in FIG. 6 isknown (refer to Patent Literature 1). In the structure, a first controlvalve 104 that adjusts the opening degree of a supply passage isprovided on the supply passage 103 connecting between a dischargechamber 101 and a control pressure chamber 102, and a second controlvalve 107 is provided on a bleed passage 106 connecting between thecontrol pressure chamber 102 and a suction chamber 105. The secondcontrol valve 107 is configured by including a spool holding concaveportion 108 formed in a housing, a spool 109 housed in the spool holdingconcave portion 108 so as to move, a back pressure chamber 110demarcated and formed behind the spool 109 in the spool holding concaveportion 108, a biasing spring 112 that biases the spool 109 in adirection away from a valve forming body 111. The spool holding concaveportion 108 is adjacent to the suction chamber 105, and leakage in thespool holding concave portion 108 from the back pressure chamber 110 tothe suction chamber 105 is suppressed to be small by a clearance betweenan inner wall of the spool holding concave portion 108 and the spool109. On a downstream of the first control valve 104 on the supplypassage 103, a fixed throttle 113 is provided, wherein an intermediateregion K between the first control valve 104 and the fixed throttle 113is connected to the back pressure chamber 110 through a branch passage114.

According to the above structure, the first control valve 104 makes asupply passage 28 in a fully closed state and the communicating statebetween the discharge chamber 101 and the control pressure chamber 102is cut off at the time of starting when a difference between a pressurePd in the discharge chamber 101 and a pressure Ps in the suction chamber105 is small. Then, a pressure Pk in the intermediate region K in thesupply passage 103 on the downstream side of the first control valve104, namely, the pressure in the back pressure chamber 110 is maintainedto be approximately the same as a pressure Pc in the control pressurechamber 102, and the spool 109 makes the bleed passage 106 in a fullyopened state by a spring force of the biasing spring 112.

As a result, even when the liquid refrigerant is accumulated in thecontrol pressure chamber 102, the pressure in the control pressurechamber 102 can be reduced earlier by releasing the pressure to thesuction chamber 105 through the bleed passage with a large openingdegree (a period of time until all the liquid refrigerant accumulated inthe control pressure chamber 102 is vaporized and discharged to thesuction chamber 105 is shortened), therefore, it is possible to avoid aninconvenience that a period of time until discharge capacity can becontrolled is increased. Therefore, the pressure Pc in the controlpressure chamber 102 is smoothly reduced by fully closing the firstcontrol valve 104 and a tilt angle of the swash plate is smoothlyincreased, thereby increasing the discharge capacity.

When the difference between the pressure Pd in the discharge chamber 101and the pressure Ps in the suction chamber 105 is increased after allthe liquid refrigerant accumulated in the control pressure chamber 102is evaporated and discharged to the suction chamber 105, the fullyclosed state of the first control valve 104 is released and the supplypassage 103 is opened, then, the pressure in the intermediate region K(pressure in the back pressure chamber 110) is increased to be higherthan the pressure Pc in the control pressure chamber 102. Then, thespool 109 moves against the biasing spring 112 and abuts on the valveforming body 111, and the bleed passage 106 is in a state of beinglargely throttled by a communicating groove 109 a formed at a tip endportion of the spool 109. Accordingly, a refrigerant amount introducedout of the control pressure chamber 102 to the suction chamber 105through the bleed passage 106 is largely reduced and the pressure Pc inthe control pressure chamber 102 is increased and the tilt angle of theswash plate is reduced, as a result, the discharge capacity is reduced.

CITATION LIST Patent Literature

Patent Literature 1: JP-A-2002-021721

SUMMARY OF INVENTION Technical Problem

In the above related-art structure, a bleed amount from the controlpressure chamber 102 to the suction chamber 105 is adjusted by the spool109 housed inside the spool holding concave portion 108 so as to slide,and the pressure in the intermediate region K between the first controlvalve 104 of the supply passage 103 and the fixed throttle 113 isallowed to act as a back pressure acting on the spool 109, therefore, itis necessary to strictly perform management of the clearance between theinner wall of the spool holding concave portion 108 and the spool 109for reducing a leakage amount of the refrigerant from the intermediateregion K (back pressure chamber 110) to the suction chamber 105 adjacentto the spool holding concave portion 108, which causes an inconveniencethat the costs are increased.

Furthermore, when the clearance between the inner wall of the spoolholding concave portion 108 and the spool 109 is set to a minute value,the leakage of the back pressure can be effectively suppressed, however,there may occur an inconvenience that contamination and so on are easilystuck into a sliding surface between the inner wall of the spool holdingconcave portion 108 and the spool 109, which may hinder movement of thespool 109 and may interfere with pressure control in the controlpressure chamber 102.

The present invention has been made in view of the above circumstancesand a main object thereof is to provide a variable-capacity compressorcapable of increasing starting performance of the compressor andeliminating a risk of the compressor becoming uncontrollable due tocontamination or the like in the refrigerant.

Solution to Problem

In order to solve the above problems, a variable-capacity compressoraccording to the present invention has a compression chamber compressingworking fluid, a suction chamber housing the working fluid compressed inthe compression chamber, a discharge chamber housing the working fluidcompressed in the compression chamber and discharged, a control pressurechamber through which a drive shaft penetrates, housing a swash platerotating with rotation of the drive shaft, a supply passage allowing thedischarge chamber to communicate with the control pressure chamber, ableed passage constantly allowing the control pressure chamber tocommunicate with the suction chamber, and a control valve adjusting anopening degree of the supply passage, in which a discharge capacity isvaried by adjusting a pressure in the control pressure chamber, whichincludes an opening passage allowing the control pressure chamber tocommunicate with the suction chamber, a valve housing chamber formed onthe opening passage, in which the opening passage is formed by includingan upstream-side opening passage allowing the control pressure chamberto communicate with the valve housing chamber, and a downstream-sideopening passage provided so as to open to one end of the housing chamberin an axial direction and allowing the valve housing chamber tocommunicate with the suction chamber, a valve body housed in the valvehousing chamber and opening/closing an opening of the downstream-sideopening passage by an end surface on one end side in the axialdirection, a biasing means for biasing the valve body in an openingdirection of the downstream-side opening passage and a pressureintroduction passage branching from a downstream side of the controlvalve of the supply passage and communicating with a region in the valvehousing chamber, which is on the opposite side of the downstream-sideopening passage with respect to the valve body housed in the valvehousing chamber.

Here, one end of the housing chamber in the axial direction indicatesone terminal end of the housing chamber when an operation direction ofthe valve body is the axial direction, and an end surface on one endside of the valve body in the axial direction indicates an end surfaceof one end portion in the operation direction of the valve body.

As described above, in the state where the compressor is suspended for along time and the pressure in the refrigerating cycle is balanced, aliquid refrigerant is accumulated in the control pressure chamber. Inthis state, the control valve allows the supply passage to be in thefully opened state, however, the valve body housed in the valve housingchamber is biased by the biasing means to make the downstream-sideopening passage in the opened state as pressures acting before and afterthe valve body is balanced.

When the compressor is started from the above state, the pressure in thesuction chamber begins to reduce to be lower than the pressure in thecontrol pressure chamber with operation at the minimum capacity in thebeginning of starting the compressor. On the other hand, the supplypassage is closed by the control valve, therefore, the pressure is notintroduced to the control pressure chamber and the housing chamber. Theevaporated refrigerant in the control pressure chamber is discharged tothe suction chamber through the bleed passage, which flows into thevalve housing chamber through the upstream-side opening passage and isdischarged from the valve housing chamber to the suction chamber throughthe downstream-side opening passage.

Accordingly, the refrigerant in the control pressure chamber can beimmediately released to the suction chamber through two systems of thebleed passage and the opening passage, and a period of time until allthe liquid refrigerant accumulated in the control pressure chamber isevaporated and discharged to the suction chamber can be shortened.

After that, when the pressure in the control pressure chamber is reducedand the discharge capacity of the compressor is increased, the pressurein the discharge chamber is increased, the closed state in the supplypassage by the control valve is released and the opening degree of thesupply passage is increased. Then, when a force acting on the valve bodyby a difference between a pressure introduced to the valve housingchamber from the supply passage through the pressure introductionpassage and a pressure in the suction chamber (force biasing the valvebody in a direction of blocking the downstream-side opening passage) ishigher than the biasing force of the biasing means, the valve body movesin a direction of closing the downstream-side opening passage to therebyclose the opening of the downstream-side opening passage by the endsurface on one end side of the valve body in the axial direction.

As the opening of the downstream-side opening passage is closed by theend surface on one end of the valve body in the axial direction, therefrigerant flowing into the valve housing chamber through the pressureinduction passage does not flow into the suction chamber regardless of aclearance between the valve body and the valve housing chamber.Moreover, the pressure introduction passage is a passage branching fromthe downstream of the control valve in the supply passage, therefore,even when the refrigerant flowing into the valve housing chamber throughthe pressure introduction passage flows back to the control pressurechamber through the upstream-side opening passage, sum totals of arefrigerant amount flowing into the control pressure chamber via thesupply passage and a refrigerant amount flowing into the controlpressure chamber via the opening passage are approximately the same,which is not an obstacle for the control of discharge capacity.

Additionally, as the pressure introduction passage branches from thedownstream side of the control valve in the supply passage and isconnected to a region in the valve housing chamber, which is on theopposite side of the downstream-side opening passage with respect to thevalve body housed in the valve housing chamber, therefore, a pressurewith less pulsation on the downstream side of the control valve can begiven in a direction of blocking the downstream opening passage by thevalve body, and the valve body inside the valve housing chamber can bepositively operated as compared with a structure where the valve bodyinside the valve housing chamber is opened and closed based on apressure in the discharge chamber with many pulsations.

As described above, the opening of the downstream-side opening passageallowing the valve housing chamber to communicate with the suctionchamber is opened/closed by the end surface on one end in the axialdirection of the valve body housed in the valve housing chamber,therefore, it is not necessary to form the valve body housed in thevalve housing chamber by the spool valve, and it is also not necessaryto strictly manage a clearance between the valve body and the valvehousing chamber.

As the use of the spool valve is avoided, there is no risk of the valvebody becoming uncontrollable due to contamination or the like in therefrigerant (movement of the valve body is not easily affected bycontamination or the like).

In the above structure, a boosting means may be provided on thedownstream side of the place where the pressure introduction passagebranches on the supply passage.

When the boosting means is provided, the pressure on the upstream sideof the boosting means can be set to be higher than the pressure in thecontrol pressure chamber, therefore, it is possible to give a higherpressure to the valve body housed in the valve housing chamber, and morestable operation can be obtained.

Moreover, a first check valve allowing only a flow from the upstreamside to the downstream side of the supply passage is used as theboosting means, thereby adjusting a pressure difference before and afterthe check valve to a prescribed value by a spring force of the checkvalve regardless of the amount of the refrigerant flowing through thesupply passage.

Furthermore, it is preferable that the valve body is formed by includinga large-diameter portion moving along an inner peripheral surface of thevalve housing chamber and a small diameter portion formed to have asmaller diameter than a diameter of the large diameter portion andopening/closing the downstream-side opening passage, and that a portionwhere the pressure introduction passage is connected to the valvehousing chamber is positioned in a region on the opposite side of thedownstream-side opening passage with respect to the large diameterportion in a state where the valve body is the most distant from thedownstream-side opening passage.

In such structure, a pressure of the refrigerant introduced into thevalve housing chamber through the pressure introduction passage can bereduced at the time of passing through a clearance between a peripheralsurface of the large diameter portion and an inner wall of the valvehousing chamber, and a strong pressing force can be given to the smalldiameter portion of the valve body by a pressure acting on the largediameter portion.

It is also preferable that a portion where the upstream-side openingpassage is connected to the valve housing chamber is positioned closerto the downstream-side opening passage side than the large-diameterportion is in a state where the valve body is the closest to thedownstream-side opening passage.

In the above structure, the pressure of the refrigerant in the controlpressure chamber flowing into the valve housing chamber through theopening passage can be positively given to the downstream side of thelarge diameter portion (the end surface on the side where the smalldiameter portion is provided), and the opening passage is not blocked bythe peripheral surface of the large diameter portion, therefore, it ispossible to avoid increase of a passage resistance in the openingpassage regardless of the position of the valve body.

It is also preferable that a second check valve allowing only a flow offluid from the control pressure chamber to the valve housing chamber isprovided on the upstream-side opening passage.

As described above, even when the refrigerant flowing from the pressureintroduction passage to the valve housing chamber flows back to thecontrol pressure chamber through the upstream-side opening passage, sumtotals of the refrigerant amount flowing into the control pressurechamber via the supply passage and the refrigerant amount flowing intothe control pressure chamber via the opening passage are approximatelythe same, which is not an obstacle for the control of dischargecapacity, however, when the refrigerant amount flowing into the controlpressure chamber through the upstream-side opening passage is increased,the refrigerant amount flowing into the control pressure chamber throughthe supply passage is reduced. The refrigerant flowing into the controlpressure chamber through the supply passage contains oil, andlubrication to sliding components inside the control pressure chamber bythe oil is expected. If the refrigerant flowing into the controlpressure chamber through the supply passage is reduced, there is a riskthat lubrication to sliding components will be insufficient.

In view of the above, when the second check valve allowing only the flowof fluid from the control pressure chamber to the valve housing chamberis provided on the upstream-side opening passage, thereby completelycutting off the backflow of the refrigerant from the valve housingchamber to the control pressure chamber and preventing the flow of therefrigerant to the control pressure chamber via the opening passage.Accordingly, it is possible to secure lubrication to the slidingcomponents inside the control pressure chamber by preventing reductionof the refrigerant amount flowing into the control pressure chamberthrough the supply passage.

Advantageous Effects of Invention

As described above, in the variable-capacity compressor according to thepresent invention in which the pressure in the control pressure chamberis adjusted through the supply passage allowing the discharge chamber tocommunicate with the control pressure chamber to adjust the openingdegree by the control valve and the bleed passage allowing the controlpressure chamber to communicate with the suction chamber, the valvehousing chamber connecting to the upstream-side opening passagecommunicating with the control pressure chamber and the downstream-sideopening passage communicating with the suction chamber is provided, andthe valve body opening/closing the downstream-side opening passage andbiased in the direction of opening the downstream-side opening passageby the biasing means is housed in the valve housing chamber. Moreover,the pressure introduction passage communicating with the portion on thedownstream side of the control valve in the supply passage is connectedto the valve housing chamber, thereby making the pressure introduced tothe valve housing chamber to act on the valve body in the direction ofblocking the downstream-side opening passage. Furthermore, the checkvalve allowing only the flow of fluid from the control pressure chamberto the valve housing chamber is provided on the upstream-side openingpassage. At the time of starting the compressor when the pressuresbefore and after the valve body (the pressure on the downstream side ofthe control valve in the supply passage and the pressure in the suctionchamber) are approximately equivalent, the valve body housed inside thevalve housing chamber maintains the opened state of the downstream-sideopening passage by the biasing means, therefore, the vaporizedrefrigerant in the control pressure chamber can be smoothly dischargedto the suction chamber through the bleed passage and the openingpassage, which can increase starting performance of the compressor.

When the pressure in the discharge chamber is increased, the controlvalve is opened and the high-pressure refrigerant is supplied to thevalve housing chamber from the supply passage through the pressureintroduction passage, and a difference between the pressure introducedinto the valve housing chamber and the pressure in the suction chamberexceeds a biasing force of the biasing means, the valve body moves inthe direction of blocking the downstream-side opening passage to blockthe opening of the downstream-side opening passage by the end surface onone end of the valve body in the axial direction. As the opening of thedownstream-side opening passage is closed by the end surface on one endof the valve body in the axial direction, the refrigerant flowing intothe valve housing chamber through the pressure introduction passage doesnot flow into the suction chamber regardless of the clearance betweenthe valve body and the valve housing chamber, and an inconvenience thatan internal circulating refrigerant is increased and performance isreduced can be eliminated.

As the valve body for opening/closing the opening passages isopened/closed based on the pressure on the downstream side of thecontrol valve as described above, the valve body inside the valvehousing chamber can be positively operated as compared with a case wherethe valve body inside the valve housing chamber is opened/closed basedon the pressure in the discharge chamber with many pulsations in thecompressor.

Additionally, it is not necessary to use the spool valve for the valvebody, therefore, it is possible to eliminate the risk of the valve bodybecoming uncontrollable due to contamination or the like in therefrigerant.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing a compressor according to thepresent invention, which is a view showing a state of a beginning ofstarting the compressor.

FIG. 2 is a cross-sectional view showing the compressor according to thepresent invention, which is a view showing a state at the time of fullstroke.

FIG. 3 is a cross-sectional view showing the compressor according to thepresent invention, which is a view showing a state at the time ofcontrolling a discharge capacity in an intermediate stroke.

FIG. 4 shows structure diagrams of an opened-state adjustment mechanismfor adjusting the opened state in opening passages, in which FIG. 4A isa view showing a state of beginning of starting the compressor and FIG.4B is a view showing a state during operation of the compressor.

FIG. 5 is a comparison table in which opened/closed states of respectivevalves and strokes of pistons are summarized according to operationstates.

FIG. 6 is a view showing a structure proposed in related art for avariable-capacity compressor.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be explainedwith reference to attached drawings.

In FIG. 1 to FIG. 3, a clutchless-type variable-capacity compressor thatis belt-driven by a power source such as an engine. Thevariable-capacity compressor includes a cylinder block 1, a rear head 3assembled to a rear side (right side in the drawing) of the cylinderblock 1 through a valve plate 2 and a front head 5 assembled so as toblock a front side (left side in the drawing) of the cylinder block 1 todemarcate a control pressure chamber 4, and these front head 5, thecylinder block 1, the valve plate 2 and the rear head 3 are fastened inan axial direction by a fastening bolt 6 to form a housing of thecompressor.

A drive shaft 7 one end of which protrudes from the front head 5penetrates the control pressure chamber (also referred to as a crankchamber) 4 demarcated by the front head 5 and the cylinder block 1. Adrive pulley 10 fitted onto a boss portion 5 a of the front head 5 so asto rotate freely through a relay member 9 attached in the axialdirection by a bolt 8 is connected to a portion of the drive shaft 7which protrudes from the front head 5, thereby transmitting rotationalpower from an engine of a vehicle through a not-shown drive belt. Oneend side of the drive shaft 7 is sealed with good airtightness betweenthe drive shaft 7 and the front head 5 through a sealing member 11provided between the drive shaft 7 and the front head 5 and supported bya radial bearing 12 so as to rotate freely. The other end of the driveshaft 7 is supported by a radial bearing 14 housed in a housing hole 13formed at approximately the center of the cylinder block 1 so as torotate freely.

In the cylinder block 1, the housing hole 13 in which the radial bearing14 is housed and plural cylinder bores 15 arranged at equal intervals ona circumference around the housing hole 13 are formed, and single-headpistons 16 are inserted into respective cylinder bores 15 so as toreciprocate.

A thrust flange 17 rotating together with the drive shaft 7 is providedsecurely to the drive shaft 7 in the control pressure chamber 4. Thethrust flange 17 is supported so as to rotate freely with respect to aninner surface of the front head 5 through a thrust bearing 18, and aswash plate 20 is connected to thrust flange 17 through a link member19.

The swash plate 20 is provided so as to move in a tilting manner arounda hinge ball 21 provided on the drive shaft 7 so as to slide, rotatingtogether in synchronization with rotation of the thrust flange 17through the link member 19. Then, engaging portions 16 a of thesingle-head pistons 16 are captively held to a peripheral edge portionof the swash plate 20 through pairs of shoes 22.

Therefore, when the drive shaft 7 rotates, the swash plate 20 is rotatedtogether, and the rotary motion of the swash plate 20 is converted intoa reciprocating straight motion of the single-head pistons 16 throughthe shoes 22, which changes capacities of compression chambers 23 formedbetween the single-head pistons 16 and the valve plate 2 in the cylinderbores 15.

In the valve plate 2, suction holes 31 and discharge holes 32 are formedso as to correspond to respective cylinder bores 15. In the rear head 3,a suction chamber 33 housing a working fluid to be compressed in thecompression chambers 23 and a discharge chamber 34 housing the workingfluid compressed and discharged in the compression chambers 23 aredemarcated. The suction chamber 33 is formed in the central portion ofthe rear head 3, communicating with a not-shown suction port connectedto an exit side of an evaporator and is capable of communicating withthe compression chambers 23 through the suction holes 31 opened andclosed by not-shown suction valves. The discharge chamber 34 is formedin a periphery of the suction chamber 33 which is capable ofcommunicating with the compression chambers 23 through the dischargeholes 32 opened and closed by not-shown discharge valves andcommunicating with a discharge space 37 formed in a peripheral wallportion of the cylinder block 1 through passages 2 a and 1 a formed inthe valve plate 2 and the cylinder block 1. The discharge space 37 isdemarcated by the cylinder block 1 and a cover 38 attached to thecylinder block 1. A discharge port 39 communicating with an inlet sideof a condenser is formed in the cover 38, and a discharge check valve 36for preventing backflow of a refrigerant from the condenser into thedischarge space 37 is provided.

A discharge capacity of the compressor is determined by strokes of thepistons 16, and the strokes are determined by a tilt angle of the swashplate 20 with respect to a surface perpendicular to the drive shaft 7.The tilt angle of the swash plate 20 is balanced at an angle in which asum total of a moment derived from a differential pressure betweenpressures of the compression chambers 23 (pressures inside the cylinderbores) acting on respective pistons 16 and a pressure in the controlpressure chamber 4, a moment derived from an inertia force of the swashplate or the pistons and a moment derived from a biasing force of adestroke spring 24 that biases the hinge ball 21 becomes “0 (zero)”.Accordingly, the piston strokes are determined and the dischargecapacity is determined.

That is, when the pressure in the control pressure chamber 4 is reduced,the differential pressure between the compression chambers 23 and thecontrol pressure chamber 4 is increased, therefore, the moment acts onin a direction in which the tilt angle of the swash plate 20 isincreased. Therefore, when the tilt angle of the swash plate 20 isincreased as shown in FIG. 2, the hinge ball 21 moves to the thrustflange side against the biasing force from the destroke spring 24, andthe stroke amounts of the pistons 16 are increased to thereby increasethe discharge capacity.

On the other hand, when the pressure in the control pressure chamber 4is increased and the differential pressure between compression chambers23 and the control pressure chamber 4 is reduced, the moment acts in adirection in which the tilt angle of the swash plate 20 is reduced.Therefore, when the tilt angle of the swash plate 20 is reduced as shownin FIG. 3, the hinge ball 21 moves in a direction away from the thrustflange 17 and the stroke amounts of the pistons 16 are reduced tothereby reduce the discharge capacity.

Then, in the present structure example, a supply passage 40 allowing thedischarge chamber 34 to communicate with the control pressure chamber 4is formed by passages 1 b, 2 b and 3 b formed over the cylinder block 1,the valve plate 2 and the rear head 3, and a bleed passage 41 allowingthe control pressure chamber 4 to communicate with the suction chamber33 is formed through the housing hole 13 formed in the cylinder block 1,a passage 1 c formed continuously from the housing hole 13, an orificehole 2 c formed in the valve plate 2 communication with the passage 1 c,a passage 7 c formed in the drive shaft 7, the clearance of the radialbearing 14 and the like.

On the supply passage 40, a pressure control valve 42 is provided, and aflow rate of a refrigrant flowing into the control pressure chamber 4from the discharge chamber 34 through the supply passage 40 is adjustedby the pressure control valve 42 to thereby control the pressure in thecontrol pressure chamber 4.

Here, the pressure control valve 42 is inserted into a mounting hole 43formed in the rear head 3, which adjusts an opening degree of the supplypassage 40 so that a suction pressure becomes a target value to therebycontrol the pressure in the control pressure chamber as well as fullyopens the supply passage 40 by stopping electrical conduction andminimizes the discharge capacity by increasing the pressure in thecontrol pressure chamber 4. In the beginning of starting, the supplypassage 40 is closed by maximizing the conductive amount (duty ratio is100%), pressure supply to the control pressure chamber is stopped orother operations are performed.

Accordingly, when the electrical conduction to the pressure controlvalve 42 is stopped in the state where the compressor is driven torotate, an internal circulation path is formed inside the compressor, inwhich the refrigerant discharged from the compression chambers 23 to thedischarge chamber 34 is circulated from the discharge chamber 34 to thesupply passage 40 (the pressure control valve 42 exists on the way), thecontrol pressure chamber 4, the bleed passage 41, the suction chamber33, the suction hole 31, the compression chamber 23, the discharge hole32 and the discharge chamber 34 in this order. Sliding components insidethe compressor is lubricated and cooled by a refrigerant gas circulatingin the internal circulation path.

In the above compressor, an opening passage 50 allowing the controlpressure chamber 4 to communicate with the suction chamber 33 isprovided. One end of the opening passage 50 is connected to the passage1 c (portion on the upstream side of the orifice hole 2 c of the bleedpassage 41) allowing the housing hole 13 formed in the cylinder block 1to communicate with the orifice hole 2 c, the other end of which isconnected to the suction chamber 33 through the valve plate 2.

In the present application of the invention, the control pressurechamber 4 includes not only a space housing the drive shaft and theswash plate but also a space where a pressure of the space housing thedrive shaft and the swash plate is directly reflected, and the passage 1c allowing the housing hole 13 formed in the cylinder block 1 tocommunicate with the orifice hole 2 c is also part of the controlpressure chamber 4.

The opening passage 50 is provided with an opened-state adjustmentmechanism for automatically adjusting the opened state of the passagealso shown as FIG. 4.

The opened-state adjustment mechanism is formed by a valve housingchamber 51 formed on the opening passage 50, a valve body 52 providedinside the valve housing chamber 51 and a spring 53 pressing the valvebody 52, having a structure in which a downstream-side opening passage50 b is opened and closed by the valve body 52 when a portion allowingthe control pressure chamber 4 to communicate with the valve housingchamber 51 in the opening passage 50 is an upstream-side opening passage50 a and a portion allowing the valve housing chamber 51 in the openingpassage 50 to communicate with the suction chamber 33 is thedownstream-side opening passage 50 b. Specifically, the valve housingchamber 51 is formed in a cylindrical shape, and the downstream-sideopening passage 50 b opens at an end portion on one end side of thevalve housing chamber 51 in the axial direction, and an opening 50 b-1of the downstream-side opening passage 50 b is opened and closed by anend surface 52 b-1 on one end side of the valve body 52 in the axialdirection (an end surface of a later-described first small diameterportion 52 b). The valve body 52 is biased in a direction of opening thedownstream-side opening passage 50 b by the spring 53 (biasing means).In the example, the valve housing chamber 51 is configured by blocking acylindrical bottomed hole formed in the cylinder block 1 by the valveplate 2, and the downstream-side opening passage 50 b is configure by athrough hole having a diameter smaller than a diameter of the valvehousing chamber 51 formed on the valve plate 2.

A pressure introduction passage 54 branching on the downstream side ofthe pressure control valve 42 of the supply passage 40 is connected tothe valve housing chamber 51 (the valve housing chamber 51 communicateswith the downstream side of the pressure control valve 42 of the supplypassage 40 through the pressure introduction passage 54). In a casewhere the valve housing chamber 51 is formed in an approximatelycylindrical shape and the downstream-side opening passage 50 b isconnected to one end portion of the valve housing chamber 51 in theaxial direction, the pressure introduction passage 54 is connected closeto an end portion on the opposite side of an end portion where thedownstream-side opening passage 50 b of the valve housing chamber 51 isconnected, and the upstream-side opening passage 50 a is connected toclose to an end portion where the downstream-side opening passage 50 bof the valve housing chamber 51 is connected.

The valve body 52 housed in the valve housing chamber 51 has a shape inwhich a suitable throttle is formed between a portion where the pressureintroduction passage 54 opens in the valve housing chamber 51 and aportion where the upstream-side opening passage 50 a opens in a state inwhich the downstream-side opening passage 50 b is blocked.

Specifically, the valve body 52 is configured by including a largediameter portion 52 a moving along an inner peripheral surface in astate where a prescribed clearance is secured between the valve body 52and the inner peripheral surface of the valve housing chamber 51, thefirst small diameter portion 52 b formed continuously from the largediameter portion 52 a to have a smaller diameter than a diameter of thelarge diameter portion 52 a and opening/closing the downstream-sideopening passage 50 b by an end surface thereof and a second smalldiameter portion 52 c formed continuously from the large diameterportion 52 a on the opposite side of the first diameter portion to havea smaller diameter than the diameter of the large diameter portion 52 a.

In the valve housing chamber 51, a portion where the pressureintroduction passage 54 is connected is a position where a pressureintroduced through the pressure introduction passage 54 acts on thevalve body 52 in a direction of blocking the downstream-side openingpassage 50 b, which is a portion to be an opposite side of thedownstream-side opening passage 50 b (first small diameter portion 52 b)with respect to the large diameter portion 52 a in a state where thevalve body 52 is positioned at the most distant position from thedownstream-side opening passage 50 b. In the example, the valve housingchamber 51 is configured so that the pressure introduction passage 54 isconnected to an peripheral surface of the valve housing chamber 51facing a peripheral surface of the second small diameter portion 52 c ofthe valve body 52 in the state where the valve body 52 is positioned atthe most distant position from the downstream-side opening passage 50 bin the valve housing chamber 51.

Furthermore, a portion where the upstream-side opening passage 50 a isconnected in the valve housing chamber 51 is a region which is on thesame side as the downstream-side opening passage 50 b (the first smalldiameter portion 52 b) with respect to the large diameter portion 52 ain a state where the valve body 52 is closest to the downstream-sideopening passage 50 b (in the state where the valve body 52 blocks thedownstream-side opening passage 50 b). In the example, the valve housingchamber 51 is configured so that the upstream-side opening passage 50 ais connected to an peripheral surface of the valve housing chamber 51facing a peripheral surface of the first small diameter portion 52 b ofthe valve body 52 in the state where the valve body 52 is positioned atthe closest position to the downstream-side opening passage 50 b in thevalve housing chamber 51.

A first check valve 60 as a boosting means is provided on the downstreamside of a place where the pressure introduction passage 54 branches inthe supply passage 40. The first check valve 60 allows only a flow fromthe upstream side to the downstream side of the supply passage 40,housing a ball-shaped valve body 60 b in a valve-body housing portion 60a provided on the supply passage 40 to allow the ball-shaped valve body60 b to be seated on a seating surface 60 c provided on the upstreamside of the valve body housing portion 60 a from the downstream side andto bias the ball-shaped valve body 60 b toward the seating surface 60 cfrom the downstream side by a spring 60 d so as to have a prescribedvalve-opening pressure.

Furthermore, the upstream-side opening passage 50 a is provided with asecond check valve 70 allowing only a flow from the control pressurechamber 4 (the passage 1 c formed in the cylinder block 1) to the valvehousing chamber 51.

The second check valve 70 houses a ball-shaped valve body 70 b in avalve-body housing portion 70 a provided on the upstream-side openingpassage 50 a to allow the ball-shaped valve body 70 b to be seated on aseating surface 70 c provided on the control pressure chamber side ofthe valve body housing portion 70 a from the valve housing chamber sideand to open/close the upstream-side opening passage 50 due to a pressuredifference between the control pressure chamber 4 and the valve housingchamber 51.

In the above example, the example in which the ball-shaped valve bodiesare used as the check valves (first check valve 60, second check valve70) provided on the upstream-side opening passage 50 a and the supplypassage 40 is shown, however, the present invention is not limited tothis.

In the above structure, the pressure Pd in the discharge chamber 34, thepressure Pc in the control pressure chamber 4 and the pressure Ps in thesuction chamber 33 are approximately equivalent in a state where thecompressor is stopped for a long period of time (while the engine isstopped), and the liquefied refrigerant stagnates in the controlpressure chamber 4. As the pressure control valve 42 is in the fullyopened state as the electrical conduction is stopped, the pressure(control valve downstream pressure Pk) in the intermediate region K ofthe bleed passage 41 (region between the pressure control valve 42 andthe first check valve 60 in the supply passage 41) is also approximatelyequivalent to the pressure Ps of the suction chamber 33. Under thisstate, the swash plate 20 is biased by the biasing force of the destrokespring 24 so that the tilt angle with respect to the surfaceperpendicular to the drive shaft 7 is the smallest. Also as shown in “atthe time of engine stop” of FIG. 5, the first check valve 60 is in theclosed state by the biasing force of the spring 60 d, the valve body 52is in the opened state by the biasing force of the spring 53, the secondcheck valve 70 is in the opened state and the discharge check valve 36is in the closed state.

When the engine of the vehicle is started from this state, rotationpower of the engine is transmitted to the drive pulley 10 of thecompressor through the drive belt even when the electrical conduction tothe pressure control valve 42 is stopped, and when the drive shaft 7 ofthe compressor is rotated, the pistons 16 reciprocate inside thecylinder bores 15 at the minimum stroke. Accordingly, an amount ofrefrigerant to be circulated inside the compressor is discharged to thedischarge chamber 34, however, the amount is not sufficient to push openthe discharge check valve 36 provided in the discharge space 37,therefore, the refrigerant is not supplied to the external refrigeratingcycle.

After that, when a switch of an air conditioner of the vehicle is turnedon, electrical conduction to the pressure control valve 42 is startedand the supply passage 40 is in the closed state (the pressure controlvalve 42 is in the closed state), the pressure is not supplied from thedischarge chamber 34 to the control pressure chamber 4, and the pressurePd in the display chamber 34 is accordingly increased. At this time, thepressure is not supplied to the control pressure chamber 4 from thedischarge chamber 34 through the supply passage 40, however, the liquidrefrigerant accumulated in the control pressure chamber 4 is continuedto be vaporized, therefore, the pressure in the control pressure chamber4 is not reduced and maintained.

Therefore, in the beginning of starting of the air conditioner and thecompressor, the pressure in the intermediate region K (control valvedownstream pressure Pk) between the pressure control valve 42 and theboosting means (the first check valve 60) of the supply passage 40 isapproximately equivalent to the pressure Ps in the suction chamber 33,which is lower than the pressure Pc in the control pressure chamber 4.As a result, a difference between the pressure on the downstream side ofthe pressure control valve 42 (control valve downstream pressure Ps) andthe pressure (Ps) of the suction chamber 33 is small, therefore, thevalve 52 is maintained in a position where the downstream-side openingpassage 50 b is opened by the biasing force of the spring 53 as shown in“beginning of starting (when the liquid refrigerant stagnates) in FIG.4A and FIG. 5. Moreover, the pressure Pc in the control pressure chamber4 is increased to be higher than the control valve downstream pressurePk, therefore, the first check valve 60 forming the boosting means is inthe closed state (the ball-shaped valve body 60 b abuts on the seatingsurface 60 c provided on the supply passage 40), which prevents therefrigerant in the control pressure chamber 4 from flowing back to thevalve housing chamber 51 through the pressure introduction passage 54.

The pressure Pc in the control pressure chamber 4 is higher than thepressure Ps in the suction chamber 33, therefore, the second check valve70 is in the opened state (the ball-shaped valve body 70 b is separatedfrom seating surface 70 c provided on the upstream-side opening passage50 a), the vaporized refrigerant in the control pressure chamber 4 flowsto the valve housing chamber 51 through the upstream-side openingpassage 50 a and flows out to the suction chamber 33 from the valvehousing chamber 51.

As described above, while the liquid refrigerant accumulated in thecontrol pressure chamber 4 is vaporized, the vaporized refrigerantcontinues to flow out to the suction chamber 33 through the openingpassage 50 in addition to the related-art bleed passage 41 flowingthrough the orifice hole 2 c, therefore, the refrigerant in the controlpressure chamber 4 can be immediately released to the suction chamber 33through two systems of the bleed passage 41 and the opening passage 50,which reduces the pressure in the control pressure chamber 4 earlier (aperiod of time until all the liquid refrigerant accumulated in thecontrol pressure chamber is evaporated and discharged to the suctionchamber is shortened to thereby avoid an inconvenience that a period oftime until discharge capacity control can be performed is extended), asa result, it is possible to increase the tilt angle of the swash plate20 smoothly and to increase the discharge capacity (FIG. 2).

When all the liquid refrigerant accumulated in the control pressurechamber 4 is evaporated and discharged to the suction chamber 33 and thecompressor makes a transition to operation at the maximum capacity, thedischarge check valve 36 is opened and the sufficient refrigerant issupplied to the external refrigerating cycle (refer to “at the time ofoperation at the maximum capacity” in FIG. 5), the temperature in theevaporator in the refrigerating cycle is gradually reduced, and thepressure Ps in the suction chamber 33 is reduced. Then, when arefrigerating ability in the evaporator reaches a sufficient value, theconduction amount of the pressure control valve 42 is adjusted and thesupply passage 40 is opened (the pressure control valve 42 is opened),and a high-pressure gas in the discharge chamber 34 is supplied to thecontrol pressure chamber 4 through the supply passage 40.

In this case, as the boosting means (first check valve 60) is providedin the downstream of the control valve of the supply passage 40, thecontrol valve downstream pressure Pk can be smoothly increased byutilizing a passage resistance generated when the refrigerant passesthrough the boosting means, thereby giving a pressure higher than thepressure Pc in the control chamber 4 to the valve body 52 housed in thevalve housing chamber 51. In the example, the boosting means isconfigured by the first check valve 60 having a prescribed valve-openingpressure as described above, thereby generating a prescribed pressuredifference before and after the boosting means regardless of the amountof the refrigerant gas passing through the supply passage 40.

Then, when a difference between the control valve downstream pressure Pkintroduced into the valve housing chamber 51 through the pressureintroduction passage 54 and the pressure Ps in the suction chamber 33 isincreased to be higher than a biasing force of the spring 53, the valvebody 52 moves in a direction of blocking the downstream-side openingpassage 50 b against the spring force of the spring 53 and makes thedownstream-side opening passage 50 b in the closed state as shown in “atthe time of an intermediate stroke (discharge capacity controloperation)” in FIG. 4B and FIG. 5.

At the same time, the refrigerant flowing into the valve housing chamber51 through the pressure introduction passage 54 passes through aclearance between an inner wall of the valve housing chamber 51 and thelarge diameter portion 52 a of the valve 52 and flows into the controlpressure chamber 4 through the upstream-side opening passage 50 a,however, the second check valve 70 allowing only the flow of fluid fromthe control pressure chamber 4 to the valve housing chamber 51 isprovided in the upstream-side opening passage 50 a, therefore, thesecond check valve 70 is in the closed state and prevents the flow ofthe refrigerant to the control pressure chamber 4 through theupstream-side opening passage 50 a.

Accordingly, the refrigerant in the control pressure chamber 4 isdischarged to the suction chamber 33 only through the related-art bleedpassage 41, and the high pressure gas is supplied to the controlpressure chamber 4 through the supply passage 40 in a state where therefrigerant amount introduced out of the control pressure chamber 4 tothe suction chamber 33 is drastically reduced, therefore, the pressurePc in the control pressure chamber 4 is smoothly increased and the tiltangle of the swash plate 20 is smoothly reduced to thereby reduce thedischarge amount (FIG. 3).

Here, in the example, the pressure introduction passage 54 is connectedto a portion of the valve housing chamber 51 on the opposite side of thedownstream-side opening passage 50 b (the first small diameter portion52 b) with respect to the large diameter portion 52 a in the state wherethe valve body 52 is the most distant from the downstream-side openingpassage 50 b, therefore, a pressure of the refrigerant introduced intothe valve housing chamber 51 through the pressure introduction passage54 can be reduced when passing through a clearance between a peripheralsurface of the large diameter portion 52 a and the inner wall of thevalve housing chamber 51, thereby generating a difference between apressure acting on one end side of the valve body 52 in the axialdirection and a pressure acting on the other end side in the axialdirection and giving a pressing force in the direction of blocking thedownstream-side opening passage 50 b against the biasing force of thespring 53.

Moreover, the upstream-side opening passage 50 a is connected to aportion to be closer to the downstream-side opening passage than thelarge diameter portion 52 a is in the state where the valve body 52 isthe closest to the downstream-side opening passage 50 b (state where thedownstream-side opening passage 50 b is blocked by the valve body 52),therefore, the refrigerant pressure Pc in the control pressure chamber 4flowing into the valve housing chamber 51 through the upstream-sideopening passage 50 a can be positively given to the downstream side inthe large diameter portion (end surface on the side where the firstsmall diameter portion 52 b is provided), and the opening passage 50 isnot blocked by the peripheral surface of the large diameter portion 52a, therefore, it is possible to avoid the increase in the passageresistance of the opening passage 50 regardless of the position of thevalve body 52.

In a case where the time of the maximum capacity operation or the timeof the discharge capacity control operation makes a transition to anidling state, the pressure control valve 42 is fully opened and thehigh-pressure refrigerant is supplied from the discharge chamber 34 tothe control pressure chamber 4 through the supply passage 40 to therebyminimize piston strokes for minimizing the discharge capacity of thecompressor as shown in “at the time of idling (clutchless offoperation)” in FIG. 5. In such case, the high-pressure gas is suppliedfrom the supply passage 40 to the valve housing chamber 51 through thepressure introduction passage 54, therefore, the valve body 52 isimmediately closed, the pressure Pc in the control pressure chamber 4 issmoothly increased, the tilt angle of the swash plate 20 is smoothlyreduced and the discharge capacity is reduced.

As described above, the valve body inside the valve housing chamber 51is controlled to be opened and closed based on the pressure on thedownstream side (control valve downstream pressure Pk) of the pressurecontrol valve 42 in the supply passage 40, therefore, the valve bodyinside the valve housing chamber can be positively operated as comparedwith a case where the valve body inside the valve housing chamber iscontrolled to be opened and closed based on a pressure in the dischargechamber 34 with many pulsations.

The flow of the refrigerant from the valve housing chamber 51 to thecontrol pressure chamber 4 can be interrupted by the second check valve70 in the case where the downstream-side opening passage 50 b is in theclosed state by the valve body 52 even when the valve body 52 does nothave the structure like spool valve, therefore, the inconvenient thatthe amount of the refrigerant supplied to the control pressure chamberis reduced through the supply passage does not occur and lubrication forslicing components inside the control pressure chamber can be secured.

Furthermore, it is possible to avoid using the spool valve as the valvebody 52 in the above structure, therefore, it is not necessary tostrictly manage the clearance between the valve body 52 and the valvehousing chamber 51, and contamination or the like in the refrigerantdoes not affect movement of the valve body.

When there is a request for maximizing the discharge capacity of thecompressor after that, the conduction amount to the pressure controlvalve 42 is increased and the supply passage 40 is closed, then, thepressure is not supplied from the discharge chamber 34 to the controlpressure chamber 4 through the pressure control valve 42. The pressurein the intermediate region K (control valve downstream pressure Pk) ofthe supply passage 40 is lower than the pressure Pc in the controlpressure chamber 4, therefore, the ball-shaped valve body 60 b in thefirst check valve 60 abuts on the seating surface 60 c and the supplypassage 40 is blocked. There are not pressure supply from the dischargechamber 34 and the backflow from the control pressure chamber 4 in theintermediate region K (a region between the downstream of the pressurecontrol valve 42 and the upstream of the boosting means), therefore, thepressure in the intermediate region K (control valve downstream pressurePk) is smoothly reduced and the pressure introduced to the valve housingchamber 51 through the pressure introduction passage 54 is also reduced.Accordingly, the valve body 52 moves to a position where thedownstream-side opening passage 50 b is opened by the spring force ofthe spring 53 as shown in FIG. 4A. Moreover, as the pressure in thevalve housing chamber 51 is lower than the pressure Pc in the controlpressure chamber 4, the second check valve 70 is opened.

Accordingly, as the refrigerant in the control pressure chamber 4 flowsto the suction chamber 33 through the upstream-side opening passage 50a, the valve housing chamber 51 and the downstream-side opening passage50 b, the pressure in the control pressure chamber 4 is smoothly reducedand the discharge capacity becomes maximum.

It is sufficient that the portion of the pressure introduction passage54 that opens to the valve housing chamber 51 has a structure in whichthe control valve downstream pressure Pk introduced to the valve housingchamber 51 acts on the valve body 52 in the direction of blocking thedownstream-side opening passage 50 b, therefore, the structure is notlimited to the example shown in FIG. 4.

In the above example, the structure in which the first check valve 60 asthe boosting means is provided on the downstream side of the place wherethe pressure introduction passage 54 of the supply passage 40 branchesis shown, however, it is also preferable that the orifice holesubstitutes for the boosting means as well as that the boosting meanscan be omitted.

REFERENCE SIGNS LIST

4 control pressure chamber

7 drive shaft

20 swash plate

23 compression chamber

33 suction chamber

34 discharge chamber

40 air feed passage

41 bleed passage

42 pressure control valve

50 opening passage

50 a upstream-side opening passage

50 b downstream-side opening passage

51 valve housing chamber

52 valve body

52 a large diameter portion

52 b small diameter portion

53 spring (biasing means)

54 pressure introduction passage

60 first check valve

70 second check valve

1. A variable-capacity compressor comprising a compression chambercompressing working fluid; a suction chamber housing the working fluidto be compressed in the compression chamber; a discharge chamber housingthe working fluid compressed in the compression chamber and discharged;a control pressure chamber through which a drive shaft penetrates,housing a swash plate rotating with rotation of the drive shaft; asupply passage allowing the discharge chamber to communicate with thecontrol pressure chamber; a bleed passage constantly allowing thecontrol pressure chamber to communicate with the suction chamber; acontrol valve adjusting an opening degree of the supply passage, inwhich a discharge capacity is changed by adjusting a pressure in thecontrol pressure chamber; an opening passage allowing the controlpressure chamber to communicate with the suction chamber; a valvehousing chamber formed on the opening passage, wherein the openingpassage is formed by including an upstream-side opening passage allowingthe control pressure chamber to communicate with the valve housingchamber, and a downstream-side opening passage provided so as to open toone end of the housing chamber in an axial direction and allowing thevalve housing chamber to communicate with the suction chamber; a valvebody housed in the valve housing chamber and opening/closing an openingof the downstream-side opening passage by an end surface on one end sidein the axial direction; a biasing means for biasing the valve body in anopening direction of the downstream-side opening passage; and a pressureintroduction passage branching from a downstream side of the controlvalve of the supply passage and communicating with a region in the valvehousing chamber, which is on the opposite side of the downstream-sideopening passage with respect to the valve body housed in the valvehousing chamber.
 2. The variable-capacity compressor according to claim1, further comprising: a boosting means provided on the downstream sideof the place where the pressure introduction passage branches on thesupply passage.
 3. The variable-capacity compressor according to claim2, wherein the boosting means is formed by a first check valve allowingonly a flow from the upstream side to the downstream side of the supplypassage.
 4. The variable-capacity compressor according to claim 1,wherein: the valve body is formed by including a large-diameter portionmoving along an inner peripheral surface of the valve housing chamberand a small diameter portion formed to have a smaller diameter than adiameter of the large diameter portion and opening/closing thedownstream-side opening passage, and a portion where the pressureintroduction passage is connected to the valve housing chamber ispositioned in a region on the opposite side of the downstream-sideopening passage with respect to the large diameter portion in a statewhere the valve body is the most distant from the downstream-sideopening passage.
 5. The variable-capacity compressor according to claim4, wherein a portion where the upstream-side opening passage isconnected to the valve housing chamber is positioned closer to thedownstream-side opening passage side than the large-diameter portion isin a state where the valve body is the closest to the downstream-sideopening passage.
 6. The variable-capacity compressor according to claim1, further comprising: a second check valve provided on theupstream-side opening passage and allowing only a flow of fluid from thecontrol pressure chamber to the valve housing chamber.